Note 11 - Share-based Compensation - Restricted Stock Units Activity (Details) - The 2014 Plan [Member]	9 Months Ended
	Sep. 26, 2020 $ / shares shares
Time-based Restricted Stock Units [Member]
Outstanding non-vested (in shares) | shares	151,725
Outstanding non-vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 3.64
Granted (in shares) | shares	362,661
Granted, weighted average grant date fair value (in dollars per share) | $ / shares	$ 2.07
Vested (in shares) | shares	(60,000)
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 4.62
Forfeited or expired (in shares) | shares
Forfeited or expired, weighted average grant date fair value (in dollars per share) | $ / shares
Outstanding non-vested (in shares) | shares	454,386
Outstanding non-vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 2.26
Performance-based Restricted Stock Units [Member]
Outstanding non-vested (in shares) | shares	240,000
Outstanding non-vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 4.81
Granted (in shares) | shares
Granted, weighted average grant date fair value (in dollars per share) | $ / shares
Vested (in shares) | shares	(40,000)
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	$ 4.38
Forfeited or expired (in shares) | shares	(200,000)
Forfeited or expired, weighted average grant date fair value (in dollars per share) | $ / shares	$ 4.89
Outstanding non-vested (in shares) | shares	0
Outstanding non-vested, weighted average grant date fair value (in dollars per share) | $ / shares